The present invention relates to a mixing device of the type having an internal mixing chamber provided with bladed rotors for mixing material, and having a separable hopper for feeding the material into the mixing chamber.
In U.S. Pat. No. 3,610,585 issued to Macleod et al and assigned to the assignee of the present invention, there is shown a mixer wherein the material is worked in the chamber under considerable pressure, and may initially consist of powders or other finely divided materials which may have a tendency to escape from the chamber. Therefore, it is desirable that the mixing chamber be adequately sealed. From time to time the chamber must be cleaned of residue and wearable parts must be replaced. It is also desirable that the apparatus be so constructed that it may be readily disassembled and reassembled. The referred to patent provides a new and improved construction which is easy to assemble, dismantle and reassemble and which provides easily replaceable parts which may be subject to wear from the mixing action.
The structure disclosed in the U.S. Pat. No. 3,610,585 further provided a hopper removably mounted onto an opening leading to the mixing chamber and a weight or plunger extending through the hopper and into the chamber to force the material to be mixed down through the hopper and into the chamber. The hopper is removably secured to the mixing chamber for the purpose of easy assembly and dismantling of the device, for reasons set forth above.
The structure discussed above has proved to be successful; however, it has been found that in some instances the fasteners employed to hold the hopper to the mixer body have a tendency to loosen during the mixing operation. This apparently occurs as a direct result of the weight which is lodged into the hopper and the mixing chamber having a tendency to be moved from side to side causing lateral motion and subsequent lateral forces against the hopper sides as well as the internal area of the mixing chamber. In the design of the mixer shown in the prior art patent herein discussed, the motion of the weight on that portion of the mixing chamber adjacent the hopper has been protected by a plurality of wear plates which extend in the mixing chamber upward to the joint at which the hopper is attached to the body of the mixing chamber. This however provides for a difference in flexibility of the walls of the hopper extending above the joint between the hopper and the mixing chamber, and that portion of the mixing chamber having the wear plates. The problem is most critical when the weight is moved upwardly into the hopper by the material being mixed, during the mixing motion.
It is therefore an object of the present invention to provide a mixing device of the type referred to having increased structural reliability over devices of the prior art.
It is a further object of the present invention to provide a mixer of the type described having means for protecting the joint between the hopper and the mixing device which further serves to protect both the mixing chamber and the hopper from excessive abrasive wear.